Process for shrinkproofing wool

ABSTRACT

LINEAR ADDITION POLYMERS HAVING MULTIPLE ALIPHATIC ISOCYANATE FUNCTIONALITY ARE EMPLOYED TO IMPREGNATE A WOOL OR WOOL-CONTAINING SUBSTRATE TO PROVIDE A TREATED SUBSTRATE EXHIBITING EXCELLENT DIMENSIONAL STABILITY CHARACTERISTICS.

Patented Aug. 27, 1974 3,832,133 PROCESS FOR SHRINKPROOFING WOOL Billy M. Culbertson, Burnsville, Edward A. Sedor, Bloomington, and William J. McKiliip, Minneapolis, Minn., assignors to Ashland Oil, Inc. No Drawing. Filed Mar. 21, 1969, Ser. No. 809,393 Int. Cl. D06m 13/42 US. Cl. 8127.6 9 Claims ABSTRACT OF THE DISCLOSURE Linear addition polymers having multiple aliphatic isocyanate functionality are employed to impregnate a wool or wool-containing substrate to provide a treated substrate exhibiting excellent dimensional stability characteristics.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the treatment of wool with a polyisocyanate to impart dimensional stability thereto.

Description of the Prior Art Considerable effort has heretofore been directed toward improving the dimensional stability characteristics of wool. Natural wool is particularly deficient in this regard and it has consequently proven to be a difficult task to ameliorate this shortcoming to the extent whereby only a tolerable degree of shrinkage is experienced after repeated washing operations. The realization of such desideratum, moreover, is complicated by the fact that the unique structure of a natural wool fiber which renders it prone to shrinkage in a washing operation or when subjected to similar environmental conditions also accounts for its overall excellent properties as a textile forming material. Thus, for any effective shrink control method to be useful in a practical sense, it must not deleteriously alter the various desirable characteristics imparted to a fabric by the wool fiber such as, hand, appearance, strength, abrasion resistance, pilling resistance and the like.

Two principal types of shrinkproofing methods have evolved in the development of this art. One of such methods is based on the chemical modification of the wool fiber. The other involves the deposition of a polymer onto the fiber surface. The latter method has been accepted as representing the more efiicacious approach in that a number of polymeric treating agents have been made available which are capable of imparting shrinkproofing properties to the wool without substantially altering the structural form of the individual fiber. The polymeric deposition method, however, generally imparts only a fugitive type of shrinkage resistance to the wool fiber since repeated washings of the fabric will inevitably result in time in the loosening and washing away of deposited polymer. This is especially so in a hot washing operation using the syndets currently in favor.

SUMMARY OF THE INVENTION In accordance with this invention, a method is provided for imparting shrinkproof properties to a wool or a woolcontaining substrate in either a fibrous or fabric form. Such method comprises impregnating the substrate with a solution or aqueous dispersion of an organic soluble linear addition polymer having a plurality of randomly distributed pendant isocyanate groups attached to carbon atoms constituting the polymeric backbone. Upon attaining a desired degree of pickup of the polyisocyanate, the substrate is heated to effect removal of the solvent or water, as the case may be.

The practice of the present invention results in the deposition of the polymeric treating agent in a manner whereby the polymer is tcnaciously bonded to the fiber surface. Thus, the above-mentioned problem associated with the prior art use of polymeric treating agents for imparting shrinkage resistance is obviated. Since wool is a proteinaceousmaterial containing active hydrogen containing groups, the permanent nature of the shrinkproofin g method of this invention is largely attributed to the reaction of the isocyanate groups of the polymeric treating agents of this invention with such active hydrogen groups thereby resulting in an advantageous degree of grafting of the polymer onto the wool.

The foremost advantages of the present invention over and above the degree and permanency of shrinkproofness imparted to the wool stems from the fact that the contemplated reactive treating agents are preformed polymers. Polymers can therefore be formulated so as to be individually suited for the treating application concerned where, in addition to imparting shrinkage resistance to the substrate, it might be desired to achieve a particular supplemental enhancement such as water repellancy, crease resistance, flame retardancy, soil release, etc. Moreover, since the treating agents of this invention are preformed polymers and not prepared in situ in the shrinkproofing process, such as is the case in the use of conventional polyisocyanates for this purpose, uniform results can be readily realized by the wool processor in the course of observing a minimum of processing details.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polymeric treating agents useful in the practice of this invention can be broadly defined as the polyisocyanates resulting from the thermolysis of a class of polyaminimides derived by the addition polymerization of tertiary amine acrylimide and a monomer copolymerizable therewith. The overall manner in which these polyisocyanates can be prepared is illustrated in the following reac tion schematic wherein R of the amine acrylimide is hydrogen, halogen or methyl and wherein A- represents a compound containing a polymerizable CH C grouping. It warrants pointing out that the formula given for the resultant polyisocyanate is meantvto indicate only the statistical distribution of the respective comonomer residues and that they are not necessarily structurally arranged in the way shown.

The above illustrated polyisocyanates are, for the most part, disclosed and claimed in copending application Ser.

No. 758,153, filed Sept. 6,1968 now abandoned. However,

manner by which such agents can be prepared will be presented herein.

As is to be noted from the schematic presented hereinabove, the base starting compound for obtaining the polyisocyanates useful as shrinkproofing agents in accordance with this invention is a tertiary amine acrylimide. Particularly exemplary of such compounds are those having the following formula:

wherein R is hydrogen, halogen, or methyl, and R is methyl or a lower hydroxy alkyl.

Amine acrylimides of the type depicted above can be conveniently prepared by two dififerent methods. One of such methods involves the reaction of an acrylate,'- preferably one having alower alkyl substitutent in the ester group, with an unsymmetrical hydrazine, e.g., 1, 'l-dimethyl hydrazine, and a lower alkylene oxide such as, for example, ethylene oxide. In accordance with the foregoing method, an applicable variation thereof consists of initially reacting the alkylene oxide with the hydrazine, whereupon the resultant hydroxy aminimide can be reacted with the acrylate in a separate step. Further details relative to the above procedures are set forth in co-pending application Ser. No. 703,554 filed Feb. 7, 1968 now US. Pat. 3,485,806.

An alternate way for producing suitable amine acrylimides consists of the classical in situ method wherein the vinyl ester, trimethyl hydrazinium salt and a strong base such as sodium methoxide, are reacted in t-butanol. As indicated, this method is known in the art.

The next step in obtaining the treating agents contemplated herein consists of copolymerizing the amine acrylimide with an active-hydrogen free comonomer containing a polymerizable CH =C group. The applicable comonomers accordingly embrace a host of vinyl and vinylidene compounds.

An exemplary enumeration of suitable vinyl and vinylidene compounds for copolymerizing with the amine methacrylimide include: the vinyl halides, e.g., vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, etc.; including the vinyl pseudo halides, e.g., acrylonitrile and methacrylonitrile; the unsymmetrical dialkyl substituted ethylenes, e.g., isobutylene, isooctene, isooctadecone; the alpha olefins, e.g., l-butene, l-hexene, l-octene, l-dodocene, l-hexadecene, l-octadecene; vinyl ethers, e.g., methyl-, ethyl-, propyl-, butyl-, isobutyl-, lauryl-, and stearyl vinyl ether; the vinyl esters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate, etc.; the aromatic vinyl compounds, e.g., styrene, alpha methyl styrene, chloro-styrene, vinyl toluene and vinyl naphthalene; the vinyl derivatives of heterocyclic compounds, e.g., vinyl pyridine, N-vinyl pyrrolidine, N- substituted N-vinyl piperidine and the N-vinyl oxazolidones; acrylamide and the N- substituted acrylamides; the acrylates, haloand methacrylates, e.g., ethyl acrylate, butyl chloro acrylate, hexyl acrylate, decyl acrylate, stearyl acrylate, behenyl acrylate, methyl methacrylate, octyl methacrylate, lauryl methacrylate, eicosyl methacrylate; the vinyl ketones, e.g., methyl vinyl ketone, hexyl vinyl ketone, lauryl vinyl ketone, etc.; the alpha, beta-ethylenically unsaturated polycarboxylic acids, esters, half esters thereof, e.g., maleic anhydride, fumaric acid, dimethyl malenate, dibutyl fumarate, dimethyl itaconate, etc.: ethylenically unsaturated fatty acids, dimers and trimers thereof, e.g., oleic acid, linoleic acids, etc.; vinyl silanes, vinyl trifluoroacetate, 2,2,2, tn'fiuoroethyl acrylate, etc.

The various comonomers can be used singly or in combination with one another.

The copolymerization of the amine acrylimide with the vinyl or vinylidene comonomer can be carried out in bulk, in solution, or in an aqueous medium. Solution polymerization is preferred insofar as a solution of the polyisocyana-te represents the preferred form for W001 treating in accordance with this invention. A variety of organic solvents can be utilized for this purpose. Both aliphatic and aromatic solvents as well as mixtures thereof with a polar solvent are applicable. Aromatics such as benzene, toluene, xylene, etc., and combinations thereof with a polar solvent; e.g., a lower alkanol, are preferred. Because of the relative stability of the aminimide grouping, elevated temperatures of as high as C. can be used in carrying out copolymerization without extensive isocyanate formation. Polymerization temperatures in excess of 100 C. may be employed; however, some rearrangement of the aminimide grouping to isocyanate will occur, either to isopropenyl isocyanate or the isocyanate on the polymer backbone.

The copolymerization can be effected by heating alone, but is preferably intiated by the use of a conventional radical forming catalyst. In some instances, it is desirable to use the free radical forming catalyst in combination with a reducing agent or promoter. Such techniques are well understood in the polymerization art.

The ratio of amine acrylimide to the comonomer or comonomers copolymerizable therewith can vary extensively depending in the main upon the particular use application envisioned for the final polyisocyanate product. There are, of course, preferred contents of the isocyanate moiety of the treating agents useful herein; however, further discussion of this aspect of the invention will be given hereinbelow. Likewise, the polymerization can be carried out or comonomers appropriately selected to produce an ultimate polymer of any desired length.

Upon obtaining the polyaminimide as outlined above, the pendant aminimide groups thereof are thermally rearranged to isocyanate groups. Thermolysis of the polyaminimide can be effected simply by heating an organic solution thereof at a temperature of between about and 200 C. and more preferably from about 120 and C. In the rearrangement of the aminimide group to an isocyanate group, a tertiary amine is evloved. Accordingly, facilitating the removal of the tertiary amine is desirable. This can be accomplished by co-distilling a fraction of the evolved amine with the solvent employed in preparing the polyaminimide in accordance with the preferred method. The extent of conversion of the aminimide groupings can be followed by noting the reduction of the infrared spectrum band at 1580 cm." and the corresponding increase of the isocyanate band at 2270 cm.- or by wet analysis of isocyanate content. Substantially complete conversion of the aminimide groups to isocyanate groups can be readily achieved in this manner. On the other hand, the extent of conversion can be controlled to retain a degree of aminimide functionality if such is desired.

The method for treating a wool substrate with the polyisocyanate in accordance with the preferred mode, commonly referred to as a padding procedure, involves immersing the substrate into an organic solution of the polymer to accomplish a desired degree of pick-up of the polymer by the substrate following the wringing thereof to remove excess solution. The amount of pick-up can be conveniently controlled by appropriately adjusting the solids content of the impregnating solution. The preferred amount of pick-up is from about l-20% based on the weight of the substrate. The solids content of the treating solution for realizing such amounts of deposition will generally be in the order of from about 1-40%. Thereafter, the impregnated substrate is dried to effect removal of the solvent. Applicable drying temperatures employing the preferred solvents range from about 100 to 150 C.

In the course of the impregnation process, it appears that the pendant isocyanate groups of the polymeric treating agent commence to graft onto the wool, presumably through the active hydrogen groups thereof, to provide a shrinkproofed material which can be subjected to repeated washings without further shrinkage occurring after the norminal degree of shrinkage experienced in the first of such washings. In view of the fact that the contemplated treating agents are aliphatic polyisocyanates, it is not necessary to temporarily inactivate or block the isocyanate groups during the treating process as is the common practice in utilizing the aromatic isocyanates for this purpose. The aliphatic polyisocyanates, however, are sufiiciently active so as to react with the wool in the absence of catalysts. If, on the other hand, it is desired to promote the reaction between the polymeric treating agent and the substrate to effect grafting through urea, urethane, etc., type linkages, a catalyst can advantageously be used; such as, for example, the dialkyltin oxides or the dialkyltin dialkoxides.

More important than the use of a catalyst in attaining a high degree of bonding of shrinkproof treating agent to the substrate is the content of the isocyanate moiety (NCO) of said agent. An applicable range of NCO content is from 0.1-50% and more preferably from about 0.5 to 5% based on the weight of the polyisocyanate. Of course, polymers containing substantially in excess of the former exemplary range can be used but any improvements realized with respect to shrinkage resistance and permanency are ordinarily not economically warranted. The polyisocyanate can be formulated so as to contain the desired isocyanate content by appropriately adjusting the ratio of the amine acrylimide to the comonomer(s) in preparing the copolymerization product, all as described hereinabove.

As indicated previously, the primary objective of this invention is to provide a method for imparting a highly permanent degree of shrink resistance to wool in the sense that the wool can be subjected to repeated washings. Not only is this objective realized but additionally the treated wool can be dry cleaned without materially affecting the degree of dimensional stability that is imparted thereto by the treating process. This represents an especially unique feature of the present invention. Moreover, the effect upon such stability of the treated wool by a dry cleaning operation can be held to a minimal value by either washing the stabilized substrate before dry cleaning or aging the substrate under ambient condition for 12 hours to 3 days before dry cleaning.

While the foregoing description of the invention has been mainly presented in terms of treating wool, it is apparent that the substrate can be a blend or a mixture with other natural fibers such as cotton and mohair or with synthetic fibers such as the polyamide, polyester, polyolefin, and acrylic fibers. In general, for optimum textile properties, the foregoing blends customarily contain an appreciable portion of the wool fiber generally over 30% by weight or more commonly 60% or higher. The substrates, moreover, can take the form of thread, yarn, woven or knitted fabric and garments.

The following working example illustrates the best mode contemplated for carrying out the present invention. As indicated, this example is provided primarily by way of illustration and accordingly, any enumeration of details set forth therein is not to be construed as limiting the invention except as such limitations appear in the appended claims. All parts are parts by weight unless otherwise noted.

EXAMPLE This example illustrates the preparation of three exemplary polymeric wool shrinkproofing agents useful in the practice of this invention and outlines the results obtained in shrinkproofing wool cloth therewith.

Polymer A Into a suitable reaction vessel equipped with a stirrer were charged 186 parts of 1,l-dimethyl-l-(Z-hydroxypropyl)amine methacrylimide, 1152 parts of n-butyl acrylate and 1560 parts xylene. With stirring the charged mixture was heated to 80 C. Four (4) parts of azobisisobutyronitrile were added whereupon the reaction mixture exothermed to 109 C., and at such temperature the exotherm was arrested by applying external cooling. After the exotherm had subsided the mixture was cooled to C. and maintained thereat for 30 minutes.

The reaction vessel was then equipped with a reflux condenser and receiver and the polymer solution thermolyzed. Thermolysis was carried out at the reflux temperature of the xylene (pot temperature 140 C.) thereby resulting in the co-distillation of xylene and amine liberated in the course of the thermolysis reaction. The solids content of reaction vessel was maintained constant by the continuous addition of make-up xylene. Thermolysis was continued for six hours. The completed polymer exhibited an isocyanate content (NCO) of 2.31% by weight. The resultant polymer solution contained 44.4% solids.

Polymer B Into a reaction vessel similar to the above were charged 23.25 parts of 1,1 dimethyl 1-(2-hydroxypropyl)amine methacrylimide, 64.0 parts n-butyl acrylate and 87.3 parts xylene. The charge was heated to C. and 2 parts of azobisisobutyronitrile added. The polymerization mixture exothermed to 140 C. whereupon it was immediately cooled to 100 C. at which temperature polymerization was carried out for an additional 30 minutes.

The polymer solution was then thermolyzed in the same manner as employed in the preparation of Polymer A to provide a polymer having 5.5% by weight isocyanate content. The solids content of the completed polymer solution was 16.5%.

Polymer C Into a similar reaction vessel as above were charged 230 parts n-butyl acrylate, 77 parts vinyl acetate, 43 parts trimethylamine methacrylimide, 4.0 parts azobisisobutyronitrile and 430 parts xylene. The charged reactants were slowly heated to 65 C. with stirring at which temperature the polymerization mass exothermed to 72 C. The vessel contents were then cooled to 65 C. and maintained at such temperature for 18 hours. An additional 0.5 part azobisisobutyronitrile was added and the polymer solution held for an additional eight hours at 70 C.

The resultant polymer solution was thermolyzed at 140 C. (pot temperature) in the same manner observed in thermolyzing the above polymer solutions. Thermolysis was carried out for six hours resulting in the polymer having 3.8% isocyanate content on a solids basis. Final non-volatile content of the solution was 23.6%.

tional treating solution was prepared of Polymer C by comparable dilution with perchloroethylene. The respective solutions were then padded on a wool cloth to the levels of dry weight pick-up indicated in Table I below. The cloth employed in the testing procedure of this example Was dyed wood flannel. After padding, the impregnated cloths were dried at C. for 15 minutes.

All of the treated samples were washed once, whereupon areas measuring 8" x 8" (aligned with the warp and filler, respectively) were marked thereon after drying. This preliminary washing is equivalent to the relaxation treatment normally given a wool fabric by the wool fabricator to compensate for the stretching occurring in the weaving operation. In this connection, it is noteworthy to mention that the control sample exhibited an area shrinkage of about 15% as compared with area shrinkage in the range of 5 to 7% for the treated cloths of this example.

The control and the treated wool samples were thereupon subjected to a cycle of five washings, dried and then measured for shrinkage and again subjected to five additional washings. One cloth test sample, employing Polymer A as indicated in Table I below, was dry cleaned after the initial washing and before commencing the initial cycle of five washings. Each laundering cycle consisted 5. A process in accordance with claim 3 wherein the of 15 minutes Washing of a four pound load in a houseamount of polymer deposited is about 1 to 20% based hold automatic washer (reversing agitator type) employon the weight of the substrate. ing a normal wash setting, medium water level and a wa- 6. A process in accordance with claim 5 wherein said ter temperature of 120 to 130 F. Sixty grams of a com- 5 substrate is in the form of a fabric. mercial heavy duty detergent composition were added in 7. A process in accordance with claim 5 wherein said each washing. Drying was accomplished in a household polymer is a thermolyzed copolymer of a tertiary amine tumbler-type dryer for 20 minutes at l48-178 F. In the methacrylimide and a monomer selected from the group instance where the test cloth sample was dry cleaned, such consisting of a C -C alkyl acrylate, a C -C alkyl methprocedure consisted of tumbling the sample for one hour acrylate, vinyl acetate, and mixtures thereof. in trichloroethylene. 8. A process in accordance with claim 7 wherein said The results obtained in this series of tests are outlined tertiary amine methacrylimide is trimethylamine methin the following Table I. acrylimide.

TABLE I Percent shrinkage alter- Pickup, 5 washes 10 washes Testrun Polywt. number mer Solvent percent Fill Warp Area Fill Warp Area Control 9.5 7 9 14 1 3 9 36.0 .0 0. 0.7 .3 0.5 .0 1.6 1.6 0.6 0,2 Perchloro- 0. 8

ethylene. do 0.4 -do 0.0

'Drycleanecl following initial washing and drying.

What is claimed is: 9. A process in accordance with claim 7 wherein said 1. A process for treating a wool or wool-containing subternary amlne methacrylimidq y ystrate to impart dimensional stability thereto which com- YP PYU methflCl'yllmldeprises impregnating said substrate with a solution or aqueous dispersion of an organic soluble linear addition poly- References Cited mer of vinyl monomers, said polymer having from about UNITED STATES PATENTS 0.1 to 50 wt. percent of randomly distributed pendant 2326 287 8/1943 cofiman isocyanate groups attached to carbon atoms constituting 2334476 11/1943 coffman "260453 the backbone thereof and drying the impregnated sub- 3282640 11/1966 Koenig g 5 K 3,485,806 12/1969 Bloomquist 26080.3 N 2. A process in accordance with claim 1 wherein said 3,527,302 9/ 1970 slagel H X carbon atoms are tertiary carbon atoms.

3. A process in accordance with claim 2 wherein said LEON D. ROSDOL, Primary Examiner polymer contains from about 0.5 to 5 weight percent of H WOLMAN Assistant Examiner the isocyanate moiety.

4. A process in accordance with claim 3 wherein the 11.5. Cl. X.R. substrate is impregnated with a solution of said polymer. -1 1 7 1 

